Online test

If attempts to connect to your PC have failed, then it simply means that your Firewall is doing is job.

Common ports: it will check the ports if this result is green it means that your ports are invisible, if they are of a different color please check the configuration of your firewall. (If everything is green it means you are invisible: you do not exist for hackers).

All services ports: this will scan all your ports from 1 to 1056 and inform you whether your firewall protects well. **As below:

Color Code:

Green: the port is invisible

Blue: the port is closed, but it is not invisible

Red: the port is OPEN! Please immediately configure your firewall, as any hacker can enter without worries!

Test your port locally (using a software)

There exist software to run on your computer even to test the ports (like "local port scan").

The reliability of the software is almost zero, because they will not check which interface ports are open (localhost, external IP, or all interfaces).

Only a test carried out by external software to your computer (such as grc.com) are to be considered.

Online tests are not 100% reliable

Online test are not guaranteed to be 100% efficient.

There are indeed techniques such as Port Knocking and Single Packet Authorization, which can open ports in a firewall without this being visible in these tests.

(That said, if tests such as grc.com tell you that your ports are closed, you can be confident more than 99%.)

Additional Information

Some softwares can help to test the firewall.

Here are the latest information I have gathered about the subject:

Once the firewall software being tested is installed, it is configured with the highest-available protection settings. The computer is connected to a closed network, with the only one other system on the network being the one we use to send the port-attacking commands to the computer.

Nmap software's port-attacking commands are used to probe all 65,535 ports of a system. A detailed report is generated for each command, which reveals the status of each port as Open, Closed, Filtered, Unfiltered, or Stealth. Stealth is the best possible status and indicates that a firewall is working well.

For unlimited offline reading, you can download this article for free in PDF format: